Presently-available image editing software programs provide the ability to “draw” on a digital image. Drawing may be performed with a digital pen or brush or some other mechanism that changes the colors in the image. Commonly, this involves “blending” a preexisting image property (e.g., color, luminosity, etc.) with data represented by the image editing tool being used. Similarly, a foreground image may be blended with a background image. The blending process may employ “blending modes.” Blending modes specify how to combine new image data, either from a tool or a foreground image, with the image data already present in the image.
A common blending mode is the “Normal” blending mode, which simply replaces the current image data with the new image data. Other pre-defined blending modes include: “Color Burn,” “Color Dodge,” “Darken,” “Difference,” “Dissolve,” “Exclusion,” “Hard Light,” “Hard Mix,” “Lighten,” “Linear Burn,” “Linear Dodge,” “Multiply,” “Overlay,” “Pin Light,” “Screen,” “Soft Light,” and “Vivid Light.” Names given to pre-defined blending modes often attempt to describe the process used to do the blend, the way the blending mode might be most commonly used, and/or an expected result of the blend.
Whatever the name, a blending mode is a specific transformation that takes two inputs (the base color (the original color in the image), sometimes called the background; and the blend color (the color used by the image editing tool or contained in a foreground image) sometimes called the foreground, and from them produces a resulting color that replaces the color in the image. Other properties such as opacity also may be used in conjunction with the blending mode to determine the resulting color. The blending mode transformation could be constructed from a continuous function or in some other way. The blending mode defines what the output will be for each potential combination of inputs.
Written descriptions have been used to communicate to a user the effect of a blending mode and to describe what it does and how it might be used. Pictorial examples may be used to attempt to demonstrate the effect of the blending mode. Such descriptions and pictures can give the user a basic idea of what the blending mode does, but they are imprecise, incomplete, and do not fully convey the transformation associated with the blending mode. Better methods are needed to fully convey the blending mode transformation to the user.
Moreover, the limited set of predefined blending modes is inadequate to produce the type of blending that a user may require. Although additional pre-defined blending modes could address this problem, no set of predefined blending modes will ever address every need. Therefore, methods are needed to enable a user to create custom blending modes.